It has long been known that cardiac arrhythmias can be treated by targeted erosion of cardiac tissue and of the conduction pathways contained therein, with such erosion being referred to as ablation. Current ablation methods include HF and RF ablation, cryoablation, laser ablation, microwave ablation, and ablation with focused ultrasound.
The HF generators used in routine clinical practice today generate a high-frequency alternating current, typically 500 kHz. A local heating effect is created by contacting tissue with the ablation catheter, to which the high-frequency signal is applied for the duration of the ablation process. This results in temperatures between 45° C. and 100° C. The result is a tissue lesion, usually having a maximum diameter of 5 mm and a depth of up to 2-3 mm. The goal of the lesion is to eliminate the previously identified arrhythmogenic substrate which is responsible for the tachycardia mechanism.
In cryoablation, the myocardial tissue responsible for the arrhythmia is supercooled in a targeted manner. Cold has been used for many decades for treating cardiac arrhythmias. Since cryotherapy freezes the cells—in contrast with the heat-based radiofrequency ablation mentioned above—it constitutes an alternative treatment option for electro-physiologists and heart surgeons.
The tip of the cryoablation catheter is cooled down to temperatures below 0° C. Heat is withdrawn from the surrounding tissue via the tip of the catheter. Depending on the catheter used, temperatures of −75° C. or even lower occur at the tip of the catheter. The patient does not perceive this cold. The myocardial cells responsible for conduction of the arrhythmia are altered by the influence of cold in such a way that they can no longer conduct the electric stimulation.
During a cardiological ablation procedure, it is necessary to check regularly, or better yet continuously, to ascertain whether the cardiac arrhythmia to be treated has been eliminated. Traditionally the success of the treatment is monitored by means of an ECG measurement and/or by intracardiac blood pressure measurement. The blood pressure measurement is of benefit in particular in ablation of tachycardiac atrial arrhythmias (atrial fibrillation, atrial flutter) because by measuring the blood pressure in the atrium, it is easy to ascertain whether the pumping function of the atria has been restored. The blood pressure measurement device is a device in addition to the traditional ablation arrangement (the ablation device and optional ECG measurement device), and requires an additional blood pressure measurement catheter placed in the atria. This blood pressure measurement catheter is necessary because the low atrial pressures cannot be measured with a traditional external blood pressure measurement.
FIG. 1 shows a device and catheter arrangement for HF catheter ablation of the traditional type. In addition to the ablation catheter 1, at least one additional EP diagnostic catheter 2 and a blood pressure measurement catheter 3 are placed in the heart of the patient 4. The ablation catheter 1 and the EP diagnostic catheter 2 are connected to an ECG measurement system 5. The ablation catheter 1 has rinsing openings, which are intended to allow liquid to be dispensed to the ablation site to cool the tissue at this site. The rinsing openings are connected to a rinsing liquid conduit 6, which is connected at its proximal end to a pump 7, which ensures the supply of liquid from a reservoir 8.
The blood pressure measurement catheter 3 is connected to a blood pressure measurement device 9. Blood pressure changes are carried outward and measured with the blood pressure measurement device 9 via the liquid column in the blood pressure measurement catheter 3.
FIG. 2 shows an atrial blood pressure curve during a sinus rhythm (a) and curves during atrial fibrillation and/or flutter (b)+(c). This shows clearly that the difference allows simple monitoring of the success of ablation.